I have 3 apparently identical brushed motors. One I bought new, one came in a model and one was given. The one I bought recently is a Graupner Speed 600, but neither of the others have labels on them, although everything else is 99.99% the same as the new one. The only obvious difference that I can see is that one of the older ones appears to have an impeller in it so that the commutator is not very visible. Am I to assume that this might be another version of the Speed 600, that needs to be cooled a bit more than a standard one? Anyone know?

Right, I hope this works! The can length is 57mm,can diameter is 35.7mm and the shaft diameter is 3.18mm. Photos are attached,fingers crossed.the motor with the impeller,if that is what it is, also has a bronze(?) front bearing, different to the other two. In one of the photos of one of the terminals there is a small wire coming out from the inside, matched by a similar wire on the other terminal. Does this signify that there are internal capacitors fitted? What does the small red plastic thing on the rear signify?

Good pics 👍At first look I would say two are identical, the 'mucky' one without the outer jacket (improves the magnetic field) is probably not. Even if it is the same type without the jacket it will not perform the same.Proof of the pudding will be in the testing, preferably with a Watt meter.The red dot signifies the positive terminal for normal (forward) rotation as brushed motors have a preferred direction due to the brush wear - Bedding In! Many don't like running backwards for long periods or at high speed. The fact that the mucky one has a gear fitted also hints that it may have different parameters. For a twin screw setup I would use the two with jackets and see how she runs with all trims set to neutral.I'll see if I can trace the type/serial number visible on the mucky one.Cheers Doug 😎

"Retirement is when you stop living at work -and start working at living/boat modeling!" 舰队的海军上将 😉 Doug

Hi ChrisThey are all based on 550 motors made by Mabuchi or Johnson. They were GP motors available in different configurations for specific purposes. You can look on data tables to find the exact specs if the motors still have visible markings.The Graupner is designed to run on 8.4volts but the motors can be wound to run on different voltages.I suspect the one with the fan is taken from an electric drill. They used to be popular with the fly boys pre brushless so they are available in large quantities at cheap prices.I suggest you run them with an ammeter connected to a 8.4 (approx) battery and see what current they draw. High current would be good for a fast runaround for 10 mins or so, low current will have more tork and be suitable for a scale cabin cruiser/tug etc.If you have two that draw roughly the same current at the same volts they might be suitable in a twin prop, provided they both rotate at the same speed.Dave

Thanks Doug. The gear you refer to is actually just part of the prop shaft universal joint which I hadn't taken off. What about the impeller visible in some of the pics through the hole in the casing and the slightly different front bearing?Does this signify a difference between that motor and the other two?

Not Quite Doug but I have a box full of motors from various sources. Mostly use Brushless nowadays as I suspect many do, but there is nothing wrong with the brushed motors and I do have many boats that run flawlessly on brushed, and in my opinion are more controllable, certainly for scale models.I once worked for a firm that stripped old computers and acquired several beautiful 24v brushed motors some with precision gearboxes. Average current draw is less than 100 Mamps. Needless to say they are German made but I have some earlier US made motors again from mainframe computers that run from 1.5 v to 24v. The tork is so great that at 12v you can't stall the motor with your fingers, but you will burn them! We used them in model tugs with 2" props.Happy daysDave

Hi DaveWow! What a treasure chest. 👍I have a few, mostly rescued from old video recorders.Next time an accu drill or screwdriver or whatever packs up must remember to strip the motor (and gears?).Many years ago in Conrad looking at their motor selection there was big box of mini low voltage motors so I, in my naivety I bought a bundle for peanuts. Several years later I realised they were surplus from vibrator dildo production! 😲 Was a pain grinding the damn weights off the shafts 🤔 You live and learn.Keep up the good works, Cheers Doug 😎

"Retirement is when you stop living at work -and start working at living/boat modeling!" 舰队的海军上将 😉 Doug

PS: we used to use 24V motors and high precision gears in our automatic tracking filters for VHF/UHF radios, until, like most things, they went digital. I still think the analogue system was better for that application. But digital is cheaper to produce 🤔Cheers Doug

"Retirement is when you stop living at work -and start working at living/boat modeling!" 舰队的海军上将 😉 Doug